1. Field of the Invention
This invention relates to a vacuum booster and more particularly to a rubber disc type reaction force apparatus for a vacuum brake booster for automobiles.
2. Description of the Prior Art
There have been developed two types of reaction force apparatuses for brake boosters. One of them is a so-called lever type and the other is a rubber disc type which is shown in U.S. Pat. No. 3,745,450 for example. The latter type is considered simpler in construction and easier to assemble as compared with the former type.
The prior art disclosed in U.S. Pat. No. 3,754,450 shows a rubber type disc disposed between the output rod and power piston. In this prior art reference, the output rod is indirectly contacted with the resinous power piston, which results in damage to the contacting surface of the resinous piston in use.